The present invention relates to a mounting system for mounting electronic assemblies on a printed circuit board, and particularly to a mounting system for successively mounting electronic assemblies on different printed circuit boards by one mounting line.
In a mounting system for mounting electronic assemblies on a printed circuit board, printed circuit boards are supplied one by one from a stocker with a number of printed circuit boards stored therein, and transported to a loader or a loading station. Then, a printed circuit board is transported to a mounting machine, and thereby electronic assemblies are attached onto the printed circuit board. The printed circuit board with the electronic assemblies mounted thereon is supplied to an unloader or an unloading station, and stored in a product stocker.
A typically mounting machine comprises an X-Y table for holding and moving a printed circuit board in the XY directions, an electronic assembly automatic attaching device for automatically attaching electronic assemblies on the printed circuit board supported by the X-Y table, and an inspection device for inspecting whether or not the electronic assembly is mounted on the predetermined position of the printed circuit board. The electronic assemblies mounted on the printed circuit board are soldered, and circuit devices are fabricated.
According to the conventional mounting system, one mounting line can handle one printed circuit board of one kind, and can fabricate circuit devices of one kind. When different circuit devices are fabricated on one mounting line, the mounting system is stopped temporarily in operation, and the process of the mounting line has to be modified, which is not economical from a time standpoint.
The stocker with the printed circuit boards stored therein can store printed circuit boards of one kind, and when different circuit devices are fabricated, the above stocker has to be exchanged to a stocker with different printed circuit boards stored therein.
Further, the conventional mounting system unavoidably produces half-finished products to cause an economical loss, which is not efficient. This defect with which the conventional mounting system encountered will be described below in detail. Let it now be assumed that four different printed circuit boards A, B, C, and D are:each used to fabricate one electric product.
When N electric products are fabricated, N four kinds of the printed circuit boards A, B, C, D have to be fabricated. However, fabricated printed circuit boards contain defects, and hence the printed circuit boards A, B, C, D fabricated as finished-products in actual practice are N.sub.A, N.sub.B, N.sub.C and N.sub.D printed circuit boards A, B, C, D. The number of electric products that can be fabricated becomes equal to the minimum value of N.sub.A, N.sub.B, N.sub.C, N.sub.D printed circuit boards A, B, C, D.
Also, let it be assumed that the minimum value of N.sub.A, N.sub.B, N.sub.C, N.sub.D of the printed circuit boards A, B, C, D is N.sub.D. Then, the number of electric products that can be fabricated is N.sub.D.
There are produced N.sub.A -N.sub.D half-finished products for the printed circuit board A, N.sub.B -N.sub.D half-finished products for the printed circuit board, and N.sub.C -N.sub.D half-finished products for the printed circuit boards C. Finally, there are produced, in total, N.sub.A -N.sub.D +N.sub.B -N.sub.D +N.sub.C -N.sub.D unfinished products.